really? even the single processor 12 core that's listed ( http://en.m.wikipedia.org/wiki/Nehalem_(microarchitecture)?wasRedirected=true ) to come out Q2 2011? I can't find your 4Ghz CPU on the list (?)
As long as it's the same stepping as the current CPUs then very possibly.
However don't get your hopes up, I'm 99% sure that CPU will NOT fit.
Edit: NO! LOL That CPU will NOT fit, it's the EX variant in a different socked and god knows what.
A faster Xeon 3600 series or 5600 series is the best your going to get